中国东北汉族一个先天性白内障家系致病基因的鉴定

目的鉴定一个先天性白内障家系的致病基因。方法根据已知与先天性白内障有关的12个致病基因的染色体上的定位,分别选取3～4个的微卫星标记位点,对该家系进行连锁分析。通过测序鉴定致病基因。结果在1q21.1GJA8位点显示最大Lod值2.44。致病基因定位于1q21.1区的GJA8基因,构成缝隙连接的缝隙连接蛋白Connexin50。DNA序列分析鉴定显示其第2外显子的第191个碱基杂合突变T>G导致其蛋白产物第64位缬氨酸转变为甘氨酸。结论Connexin50的V64G新生突变是导致该家系的致病原因。

A heterozygous transversion of connexin 50 in a family with congenital nuclear cataract in the northeast of China

Objective To identify the genetic defect causing autosomal dominant congenital cataract (ADCC) in a five-generation family in the northeast of China. Methods Linkage analysis was carried out with ploymorphic microsatellites on the Human MapPairs marker set, special known loci. Mutation analysis of the candidate gene in the critical region was performed to detect the potential mutation. Results ~The maximum Lod score (2.44 at recombination fraction theta=0) was obtained for markers D1S498,D1S305, and D1S2844.The cataract locus in this family constellation was mapped to 1q21.1 and 21.44 cM interval between D1S2344 and D1S2844, which were known to flank the gene coding Connexin 50 (Cx50) or gap junction protein alpha-8 ~( GJA8). Sequencing of the coding region of GJA8 gene showed a heterozygous transversion T>G in exon 2, which resulted in the substitution of glycine for valine at amino acid 64, and this position was in the first connexin signature region that characterized this protein. Conclusion This is the first report on a mutation in the first connexin signature region of the GJA8 and a different mutation within Cx50 revealed in this family, which might account for the phenotypic differences observed. Furthermore, this study confirmed that GJA8 plays a vital role in the maintenance of human lens transparency.